The present invention relates generally to a chair, in particular a work chair, which has a seat shell provided with a cushion, wherein the front edge of the cushion extends outwardly beyond the front edge of the seat shell.
Persons must sit on work chairs over a long time. Since the long seats are not convenient for long time sitting, it is for example important when the seat support ergonomically supports the thighs. In other words, the seat surface must be dimensioned as to its depth so that it supports the thighs over its whole length, but does not press in the knee hollow when the pelvis abuts against the back rest. Since the chairs as a rule are made in accordance with predetermined standards, it is possible that for persons whose thighs lengths do not correspond to the standards can sit on the chair with less comfort. Moreover, frequently a chair is used by several persons of different body sizes, for example during layer exchange. Standard chairs are not identically convenient for sitting of all users. In order to eliminate these problems, chairs, in particular work chairs are equipped with a seat depth adjustment. Seats with a seat depth adjustment have preferably a telescopic extension formed so that moving the extension in or out provides a corresponding individual adjustment of the supporting surface for the thighs. A full surface support of the cushion and thereby of the thighs is however possible in this construction only with very high expenses.
Accordingly, it is an object of the present invention to provide a chair of the above mentioned general type, which with a simple construction, provides a seat depth adjustment which is also easy to operate.
In keeping with these objects and with others which will become apparent hereinafter, one feature of present invention resides, briefly stated, in a chair, in which the front edge of the cushion is mounted on an actuating element which is connected with a shaft arranged under the seat surface, and at least one toothed disc is arranged on the shaft over which an endless belt or an endless chain is guided, the belt or the chain are fixedly connected with the seat shell and a second toothed disc which is displaceable together with the first toothed disc parallel to the seat shell is guided so that, by raising or pressing down of the actuating element, the front edge of the cushion is displaceable forwardly or rearwardly.
When the chair is designed in accordance with the present invention, then a seat depth adjustment is implemented in a simple structural way and simultaneously can be easily operated by the user.
Preferably, the shaft with the at least one first toothed disc and with the at least one second tooth disc is arranged on a common component, which is displaceable relative to the seat shell and is supported on it.
The component can be for example a web with a front edge which supports the shaft with the first toothed disc, and with a rear edge which supports the second toothed disc.
The web can be mounted on a bushing which is guided on a rod connected with the seat shell. This provides for a simple construction.
The endless toothed belt or the endless chain can be arrestable by deviating rollers. Thereby a person who sits on the chair can not displace inadvertently with the legs the supporting surface for the thighs.
For the same purpose or when desired as an additional feature, the rod and the bushing can be arrestable with one another by the endless toothed belt or the endless chain arrestable by the deviating rollers.
For an improved guidance of the seat depth adjustment, correspondingly left and right from the center of the seat shell, two first toothed discs can be arranged on the shaft. An endless toothed belt or an endless chain can be guided in this manner.
The shaft can be formed as a hexagonal edge shaft, and a hexagonal opening can be provided on the toothed discs mounted on it. Thereby the force transmission from the actuating element to the toothed discs is ensured in a reliable manner by a form-locking connection.
The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.